1. Field of the Invention
The present invention relates to a capacity estimating system and method for a rechargeable storage battery of an automobile and, more specifically, to a capacity estimating system and method capable of accurately estimating and displaying a remaining capacity of a battery, i.e., a remaining amount of dischrgeable electric energy in a battery, regardless of a state of degradation of plates or electrolyte temperature.
2. Description of the Prior Art
Rechargeable storage batteries are used in a wide variety of applications in automobiles, such as electrical power sources for auxiliary equipments, lighting equipments, or propulsion power sources for electric vehicles. Therefore, it is important for a vehicle operator to monitor a remaining capacity of a battery (referred to as "battery capacity" hereinafter), because he or she can know when a battery should be replaced with a new one next, or in case of an electric vehicle, when and where batteries should be recharged next.
There have ever been proposed miscellaneous technologies to estimate a battery capacity of a vehicle battery. Among them, Japanes patent application laid-open No. 26587 (1988) discloses a technology in which a battery capacity is predicted by referring to a charging/discharging characteristic map of the vehicle battery based on values of voltage, current and time during charging and discharging of battery.
However, in this prior art, when positive or negative plates of batteries are deteriorated, since an actual degree of deterioration of the battery plates is not reflected accurately, estimation accuracy of the battery capacity becomes low. Further, when temperature of electrolyte is high, the battery capacity tends to be estimated to be higher than an actual one.